Added initial classes in our new infra structure
create incomplete methods for the AI, attach it to the zombie
added health to entities
refactored input handlers
Merge branch 'dev' into zombies
fixed bug created by instantiating the sprite after calling physics on it
added render on entity, removed from camera
Merge branch 'zombies' into dev
did a bunch of refactoring
Made UnitAI a subclass of MovementAI
Made zombie movement AI a subclass of movement AI
added simple working zombie follow ai
added a method to create a zombie in the entity manager
update camera handler to use the new entity manager method
change selection handler to use instance of unit so it skips camera and zombies.
added a few test zombies to main.js
Merge branch 'dev'